Variabilidad morfométrica en crustáceos de playas arenosas de la Isla Grande de Chiloé, sur de Chile

Indexación: Web of Science; Scielo.The macroinfauna of exposed sandy beaches along the Chilean coast is dominated by crustaceans, which show an across-shore zonation; the talitrid amphipod Orchestoidea tuberculata as the dominant taxon in the upper levels, the cirolanid isopod Excirolana hirsuticauda is dominant in the mid-intertidal, and the anomuran crab Emerita analoga is common in the low levels. This study analyses samples collected during the spring of 2001 and 7 morphological characters were measured on 30 adults of each species: body length, body height, body width, antennae and uropodal exopod lengths. The study sites were located near 42°S, an area where various beach types (i.e., reflective, intermediate and dissipative) occur along the northern coasts of the Chilean archipelagos. The morphometric variability of O. tuberculata, E. hirsuticauda and E. analoga was analyzed using cluster and principal component analysis. The results of this study showed that independently of beach type, individuals of O. tuberculata inhabiting proximal beaches showed greater similarity than individuals inhabiting beaches located distant from each other. Individuals of E. analoga inhabiting similar beach types showed greater similarity than individuals living in different beach types. These results are discussed in relation to across-shore zonation and the natural history of these species.La macroinfauna de playas arenosas expuestas en la costa chilena está dominada por crustáceos, los cuales muestran una zonación transversal; el anfípodo talítrido Orchestoidea tuberculata es el taxón dominante en los niveles superiores, el isópodo cirolánido Excirolana hirsuticauda lo es en la parte media del intermareal y el anomuro Emerita analoga es dominante en los niveles bajos. Este estudio examinó la variabilidad morfométrica de estas 3 especies de crustáceos en relación a los tipos morfodinámicos de playas. Las muestras fueron recolectadas durante la primavera de 2001 y se examinaron 7 caracteres morfológicos medidos en 30 adultos de cada especie: longitud del cuerpo, alto del cuerpo, ancho de cuerpo, longitud de las antenas y longitud de los urópodos. Los sitios de estudio se localizaron cerca de los 42°S, un área donde los diferentes tipos de playa (i.e., reflectivo, intermedio y disipativo) se producen a lo largo de las costas septentrionales de los archipiélagos chilenos. La variabilidad morfométrica de O. tuberculata, E. hirsuticauda y E. analoga se analizó mediante análisis de cluster y de componentes principales. Los resultados de este estudio mostraron que, independientemente del tipo de playa, los individuos de O. tuberculata que habitan playas próximas presentan una mayor similitud que con aquellas que habitan playas lejanas. Los individuos de E. analoga que habitan en el mismo tipo de playa mostraron una mayor similitud que con aquellas que habitan en diferentes tipos de playas. Estos resultados se discuten en relación con la zonificación a través del intermareal y la historia natural de estas especies.http://ref.scielo.org/rcysp

Outer rise seismicity related to the Maule, Chile 2010 mega-thrust earthquake and hydration of the incoming oceanic lithosphere

Most of the recent published geodetic models of the 2010 Maule, Chile mega-thrust earthquake (Mw=8.8) show a pronounced slip maximum of 15-20 m offshore Iloca (similar to 35 degrees S), indicating that co-seismic slip was largest north of the epicenter of the earthquake rupture area. A secondary slip maximum 8-10 m appears south of the epicenter west of the Arauco Peninsula. During the first weeks following the main shock and seaward of the main slip maximum, an outer rise seismic cluster of >450 events, mainly extensional, with magnitudes Mw=4-6 was formed. In contrast, the outer rise located seaward of the secondary slip maximum presents little seismicity. This observation suggests that outer rise seismicity following the Maule earthquake is strongly correlated with the heterogeneous coseismic slip distribution of the main megathrust event. In particular, the formation of the outer-rise seismic cluster in the north, which spatially correlates with the main maximum slip, is likely linked to strong extensional stresses transfered from the large slip of the subducting oceanic plate. In addition, high resolution bathymetric data reveals that bending-related faulting is more intense seaward of the main maximum slip, where well developed extensional faults strike parallel to the trench axis. Also published seismic constraints reveal reduced P-wave velocities in the uppermost mantle at the trench-outer rise region (7.5-7.8 km/s), which suggest serpentinization of the uppermost mantle. Seawater percolation up to mantle depths is likely driven by bending related-faulting at the outer rise. Water percolation into the upper mantle is expected to be more efficient during the co-seismic and early post-seismic periods of large megathrust earthquakes when intense extensional faulting of the oceanic lithospher

Evolution of the seismic structure of the incoming/subducting oceanic Nazca Plate off South Central Chile

The release of fluids in subduction zones is believed to be an important process controlling earthquakes both in the downgoing plate and in the seismogenic megathrust fault zone. Depending on the depth of slab dehydration, water may nurture rupture propagation and trigger arc magmatism. Growing number of geophysical evidence suggest that alteration and hydration of the oceanic plate is most vigorous at the trench-outer rise, where extensional bending-related faulting affects the hydrogeology of the oceanic crust and mantle. To better understand the processes of hydration and alteration affecting the oceanic lithosphere prior to and during subduction, I have studied the seismic velocity structure of the oceanic Nazca plate offshore of southern central Chile. A combination of swath bathymetric, wide-angle and reflection seismic data was used to derive 2D velocity-depth models, using joint refraction and reflection travel-time tomography along two main corridors: (i) offshore Isla de Chiloe (~43°S) and (ii) southern Arauco peninsula (~38°S). The study area corresponds to the southern central accretionary Chile margin, where the trench is heavily filled with up to 2.2 km of sediments. The velocity models show P-wave velocities typical for mature fast-spreading crust in the seaward section of the profiles, with uppermost mantle velocities as fast as 8.3-8.4 km/s. Approaching the Chile trench seismic velocities are significantly reduced, however, suggesting that the structure of both the oceanic crust and uppermost mantle have been altered, possibly due to a certain degree of fracturing and hydration. The decrease of the velocities roughly starts at the outer rise; ~100 km from the deformation front, and continues into the trench. Anomalously low heat flow values near outcropping basement highs were founded at the outer rise offshore Isla de Chiloe, suggesting an efficient inflow of cold seawater into the oceanic crust. Hydration and crustal cracks, activated by extensional tectonic stresses, are suggested to govern the reduced velocities in the vicinity of the trench. Considering typical flow distances of 50 km, water might be redistributed over most of the trench-outer rise area. In addition, Poisson's ratios at the lowermost crust and uppermost mantle reach values of ~0.26 and ~0.29, respectively. These features can be explained by an oceanic crust partially weathered, altered and fractured. Relatively high Poisson's ratios in the uppermost mantle may be likely related to partially serpentinized mantle. On the other hand, the comparison of the uppermost mantle P-wave velocities at the crossing point between perpendicular profiles at ~43°S (~90 km seaward from the trench axis) reveals a low degree of Pn anisotropy (<2 %). Offshore southern Arauco peninsula, the Mocha Fracture Zone is obliquely subducting underneath the South American plate and coincides with an area of even slower velocities and thinning of the oceanic crust (10-15 % thinning), suggesting that the incoming fracture zone may enhance the flux of the chemically-bound water into the subduction zone. The low $P_n$ velocities found in the outer rise area span along the subducting plate and reach a maximum depth of 6-8 km in the uppermost mantle, suggesting that as the oceanic plate subducts at the trench, bending and faulting continues to affect the oceanic lithosphere. The restoring to 'normal' mantle velocities of ~8.4 km/s coincide with the 400-430°C isotherm. This depth is interpreted as the depth limit of hydro-alteration within the upper part of the oceanic lithosphere, where extensional stresses dominate

Beyond the Grand Tour: re-thinking the education abroad narrative for US higher education in the 1920s

This paper utilizes primary source documents from the first officially sanctioned US study abroad programs in the 1920\u27s to argue that the discourse about the first study abroad programs for US students was a break from the Grand Tour tradition of the eighteenth and nineteenth centuries. Instead, this paper suggests that study abroad represented an experimental and innovative approach to the acquisition of knowledge for US undergraduates. The discourse of those who created these programs and those who participated was distinct from the Grand Tour in three ways that are described in the paper as, distinct by design, distinct by omission and distinct by experience. These three areas of distinction refute the contemporary narrative that conflates the Grand Tour with study abroad

Designing industry structure and regulation under political economy constraints.

This thesis focuses on the political economy of industrial policy as defined by Laffont (2000). In particular we study the effects of political economy constraints on industry design. Our motivation relies on the results of more than 20 years of regulatory reforms, where industries have been reorganised after their initial privatisation and/or restructure. So far, the literature has extensively studied the relationship between political economy and regulation (Levy &; Spiller (1997); Henisz & Benet (2003)). However, the study of the relationship between political economy and industry structure has received less attention. This has happened despite the fact that, as noted by Dana (1993), industry structure and regulation are jointly determined. Our work contributes to the study of the effects of political economy constraints on industry design. At a theoretical level we build on Auriol & Laffont (1992)'s model of regulation by duopoly and on Dana (1993)'s model of regulating multiproduct natural monopolies. We introduce delegation to their problem and we allow for regulatory capture. In the first case we found that under some circumstances capture biases Congress' decision towards a more competitive structure (duopoly) as the optimal response. In the second case, we find that if preventing capture is too costly, industry design favours horizontal separation of the natural monopolies as the optimal response. At an empirical level, we analyse the political economy constraints that led the Mexican government to reform its natural gas industry while keeping natural gas production as a legal monopoly and organising the industry with a dominant integrated incumbent (transmission and retail). This chapter contributes to our research by opening the "black box" of the determinants of industry design a little more. It also contributes to the literature that has studied Mexican natural gas reform. This literature has concentrated its attention on the study of regulatory incentives, taking industry structure as given

Exteme Variables in Star Forming Regions

The notion that low- to intermediate-mass young stellar objects (YSOs) gain mass at a constant rate during the early stages of their evolution appears to be challenged by observations of YSOs suffering sudden increases of the rate at which they gain mass from their circumstellar discs. Also, this idea that stars spend most of their lifetime with a low accretion rate and gain most of their final mass during short-lived episodes of high accretion bursts, helps to solve some long-standing problems in stellar evolution. The original classification of eruptive variables divides them in two separate subclasses known as FU Orionis stars (FUors) and EX Lupi stars (EXors). In this classical view FUors are at an early evolutionary stage and are still gaining mass from their parent envelopes, whilst EXors are thought to be older objects only surrounded by an accretion disc. The problem with this classical view is that it excludes younger protostars which have higher accretion rates but are too deeply embedded in circumstellar matter to be observed at optical wavelengths. Optically invisible protostars have been observed to display large variability in the near-infrared. These and some recent discoveries of new eruptive variables, show characteristics that can be attributed to both of the optically-defined subclasses of eruptive variables. The new objects have been proposed to be part of a new class of eruptive variables. However, a more accepted scenario is that in fact the original classes only represent two extremes of the same phenomena. In this sense eruptive variability could be explained as arising from one physical mechanism, i.e. unsteady accretion, where a variation in the parameters of such mechanism can cause the different characteristics observed in the members of this class. With the aim of studying the incidence of episodic accretion among young stellar objects, and to characterize the nature of these eruptive variables we searched for high amplitude variability in two multi-epoch infrared surveys: the UKIDSS Galactic Plane Survey (GPS) and the Vista Variables in the Via Lactea (VVV). In order to further investigate the nature of the selected variable stars, we use photometric information arising from public surveys at near- to farinfrared wavelengths. In addition we have performed spectroscopic and photometric follow-up for a large subset of the samples arising from GPS and VVV. We analyse the widely separated two-epoch K-band photometry in the 5th, 7th and 8th data releases of the UKIDSS Galactic Plane Survey. We find 71 stars with _K > 1 mag, including 2 previously known OH/IR stars and a Nova. Even though the mid-plane is mostly excluded from the dataset, we find the majority (66%) of our sample to be within known star forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (27 stars). The analysis of the multi-epoch K-band photometry of 2010-2012 data from VVV covering the Galactic disc at |b| < 1◦ yields 816 high amplitude variables, which include known variables of different classes such as high mass X-ray binaries, Novae and eclipsing binaries among others. Remarkably, 65% of the sample are found concentrated towards areas of star formation, similar to the results from GPS. In both surveys, sources in SFRs show spectral energy distributions (SEDs) that support classification as YSOs. This indicates that YSOs dominate the Galactic population of high amplitude infrared variable stars at low luminosities and therefore likely dominate the total high amplitude population. Spectroscopic follow-up allows us to confirm the pre-main sequence nature of several GPS and VVV Objects. Most objects in both samples show spectroscopic signatures that can be attributed to YSOs undergoing high states of accretion, such as veiling of photospheric features and CO emission, or show FUor-like spectra. We also find a large fraction of objects with 2.12 μm H2 emission that can be explained as arising from shock-excited emission caused by molecular outflows. Whether these molecular outflows are related to outbursts events cannot be confirmed from our data. Adding the GPS and VVV spectroscopic results, we find that between 6 and 14 objects are new additions to the FUor class from their close resemblance to the near-infrared spectra of FUors, and at least 23 more objects are new additions to the eruptive variable class. For most of these we are unable to classify them into any of the original definitions for this variable class. In any case, we are adding up to 37 new stars to the eruptive variable class which would double the current number of known objects. We note that most objects are found to be deeply embedded optically invisible stars, thus increasing the number of objects belonging to this subclass by a much larger factor. In general, objects in our samples which are found to be likely eruptive variable stars show a mixture of characteristics that can be attributed to both of the optically-defined classes. This agrees well with the recent discoveries in the literature. Finally, we are able to derive a first rough estimate on the incidence of episodic accretion among class I YSOs in the star-forming complex G305. We find that _ 9% of such objects are in a state of high accretion. This number is in agreement with previous theoretical and observational estimates among class I YSOs

Emotion Regulation Strategies on Depression through a Problematic Use of Technology: Toward an Explanation of the Association between Depressive Symptomatology and Internet Addiction

Depression has been reliably associated in the past with uncontrolled use of the Internet regardless of its consequences, a phenomenon commonly referred to as Internet addiction. However, less attention has been afforded to explaining this association. The present study aims to provide a potential explanation based on current theoretical accounts of emotion regulation and the problematic use of the Internet. To achieve this goal, this dissertation comprises three articles. The first discusses a transcultural adaptation of the most psychometrically evaluated measure of Internet addiction and a test of its psychometric properties on an adult sample from Chile. Next, using a sample of Chilean high school students, a cross-sectional test of two potential mechanisms linking depressive symptomatology and Internet addiction investigates the possibility of being cognitively absorbed on the Internet (referred to as flow experiences online) and using the Internet to postpone unpleasant tasks (referred to as Internet procrastination). The final article analyzed data from the follow-up measurements of the adolescent sample to provide a longitudinal explanation of the association between depressive symptomatology and Internet addiction for those using the Internet to disconnect from life situations, that is, using the Internet as a proxy for an attentional deployment emotion regulation strategy. Taken together, results suggest that the inflexible use of the Internet to regulate emotional experiences may influence the development of Internet addiction based on a negative affective state such as the presence of depressive symptomatology. A possible vicious circle is theoretically discussed, together with the study limitations and potential implications for both clinical practice and future research efforts. It is hoped that the present study sheds light on the mechanisms linking the technologically mediated context with adolescent affective processes

CAP Chronicles: A Retrospective Look at the Violence Prevention Initiative's Community Action Programs

Summarizes an evaluation of an initiative that took a public health approach to youth violence, working with academics, residents, social service providers, and policy makers. Focuses on the impact and strategies of local Community Action Programs (CAP)